Method for making iron oxide



Dec. 25, 1945. Q MANN 2,391,723-

METHOD FOR MAKING IRON OXIDE Filed Feb. 17, 1941 4 Sheets-Sheet lINVENTOR CE-CIL A. MANN ATTOR 5Y5 Dec. 1945. Q M 2,391,723

METHOD FOR MAKING IRON OXIDE Filed Feb. 17, 1941 4' sheets-sheet 2INVENTOR cecn. A. MANN BY j ORNEQf Dec. 25, 1945. I c. A. MANN 2,391,723

METHOD FOR MAKING IRON OXIDE 1 Filed Feb. 17, 1941 4 Sheets-Sheet 3INVENTOfi ce-cu. A7 ma N {L24 TTORNE Y8 Dec. 25, 1945 t r c. A. MANN 3 7METHOD FOR MAKING IRON OXIDE Filed Feb. 17, 1941 4 Sheets-Sheet 4 mVENTOR E 5511 F7. lflann BY m%%% %4' A TTORNE YE Patented Dec. 25, 1945METHOD FOR MAKING IRON OXIDE Cecil A. Mann, Dayton, Ohio, assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareApplication February 17, 1941, Serial No. 379,166

6 Claims.

This invention relates to a method and apparatus for making finelydivided iron oxide powder and is particularly concerned with the methodand apparatus wherein iron is oxidized and simultaneously comminuted.

The main object of the invention is to provide a method and apparatusfor making iron oxide powder of a predetermined particle size in aneconomical manner, wherein the steps of oxidizing the iron andcomminuting the iron are accomplished simultaneously. In carrying outthe above object, it is a further object to supply iron either inrelatively small particles, or'as a molten fluid to a generally-circularaxially-confined vortex chamber and causing said iron to rotate at ahigh rate of speed therein by the injection of high pressure, hightemperature steam supplied adjacent the periphery of the chamber,whereby the particles of iron are oxidized by the steam andsimultaneously, due to centrifugal force, are impinged at a high rate ofspeed against the peripheral walls of the chamber whereupon the oxidecoating is broken off and wherein the particles of iron are againoxidized while the oxide particles are further comminuted. The rotatingfluid within the chamber further causes a centrifugal classifying actionof the particles wherein the fine particles which must necessarily besubstantially of oxide move inwardly and pass off from the chamber at aninward point thereof.

Another object of the invention is to provide a method and apparatus forproducing finely divided iron oxide powder wherein relatively smallparticles of iron are fed into a suitable apparatus for comminuting theiron which is maintained at a relatively high temperature and whichincludes an oxidizing fluid therein whereby the surface of the iron isoxidized and progressively is broken off to present new surfaces foroxidation while the oxide broken off is comminuted. The particles may beclassified by an air blast or other well-known classifying methods.

In carrying out the above object it is a further object to provide aball-mill, or a rod-mill as the apparatus is to accomplish the desiredresult wherein the exterior of the mill is preferably heated and whereinsteam or another oxidizing fluid is injected within.

A further object of the invention is to utilize the iron oxide formed inthe process as a starting point in the manufacture of sponge ironparticles wherein the highly comminuted oxide particles are deoxidizedto form the sponge iron.

Further objects and advantages of the present invention will be apparentfrom the following do with another method of making .a powdersimdescription, reference being had'to the accompanying drawings whereinpreferred embodiments of the present invention are clearly shown.

In the drawings:

Fig. 1 is a partial fragmentary plan view of one type of apparatus whichmay be used to accomplish oxidation and'comm'inution 011mm and ironoxide.

Fig. 2 is a sectional view taken 0? Fi 1.

Fig. 3 is a partial fragmentary plan view of another embodiment of theapparatus which may be used.

FiFig. 4 is a sectional view taken on line 4-4 of Fig. 5 is a partialfragmentary view of another embodiment of operations to carry out theoxidation and comminution of iron and iron oxide.

Fig. 6 is a modification of the apparatus shown in Fig. 5, and

Fig. 7 is a flow chart showing the steps in the process of making spongeiron powder together with an alternative process as to certain of thesteps.

The manufacture of sponge iron powder has heretofore presented numerousdifiiculties in that from an economic standpoint the oxidation of smallparticles ofiron requires relatively long periods of time. Thisoxidation is necessary for two reasons. First, it is relativelydifficult to comminute iron due to the fact that it is not friable innature but ductile and therefore usual comminution methods merely changethe shapes of particles without breaking them. up. Second, iron powdermade from anything but iron oxide is not of a spongy nature, whichcellular structure of the particles is highly desirable. In the on line2-2 'past, methods have been proposed wherein iron is embrittled due tothe inclusion of combined carbon whereby the particles are brittle andmay be comminuted by conventional disintegrating methods. Thisembrittled iron'in comminuted form is then decarburized. This processhowever does not produce iron of a spongy character. The process isdisclosed in the Clements et al. Patent 2,164,198 assigned to theassignee of the present'application. 1

A method for making sponge' iron powder wherein the iron'is firstdecarburized, then oxidized, and then comminuted inv separate steps isdisclosed in my copendingapplication Serial No. 363,339, filed October29, 1940, now matured into Patent No. 2,237,867, and assigned to theassignee of the present invention. This application vhasto Disin IReferring particularly to Fig. 1, a generally cir cular axially confinedvortex chamber is shown at 20 which includes an inclined circularcentral wall 22 which preferably has serrations 24 thereon to aid in theattrition of particles impinging thereon. The outer wall may also beserrated if desired. The annular circular wall 22 forms a d scharge portfor the chamber as noted at 26 and when material has reached the desiredreduced size as predetermined bv various calculations. it

will pass off from chamber 20 through the discharge port to a col ector28. whence it may be removed. either continuouslv or intennittentlv. andpassed through a suitable deox dizing furnace. not shown. The chamber 20has disposed around the peri hery thereof a pluralitv of iniection ports30 throu h which steam under igh pressure and at a hieh tem erature isadmitted to the chamber. The ports 30 a e fed from manifold 3| and are al directed o that the str am of injected steam follows a path subsantially tangential to an ima ina y r-ircle having a radius ofapproximately one-half the radius of t e chamber. In this manner the inected fluid'rotates within the chamber so that the ath having thegreatest ra e of rotati n is substantial y the ima inary ci cle in thecenter of t e chamber. Above each of sa d injection ports 30 there is afeeding port 32. The p rts 32 are used for introducing the material tobe disinte rated into the chamber. The po ts 32 are so disposed thatmaterial introduced tberethron h falls directly into the stream of fluidbein iniected from ports 30, In

varied to accomplish comminution to the desired particle size.

The particles of iron fed into the chamber 20 through ports 32, asheretofore described, are preferably formed by melting iron ingots orscrap,

or steel scrap under decarbonizing conditions so that the iron issubstantially pure and then pouring' this iron into a stream of fluidsuch as water whereupon it is quickly cooled and simultaneously brokenup into relatively small sized particles resembling shot. It is thisshot that is fed to the disintegrator. Obviously, the iron may includesome alloying ingredients such as manganese, nickel, vanadium,molybdenum, or other conventional ingredients found in steel, if steelhappens to be the starting product.

I further propose to use all of the aforementioned steps simultaneouslyas shown in apparatus illustrated in Figs. 3 and 4. In this instance,the chamber 38 is similar to chamber 20 of Fig. 1 and includes aplurality of injection ports 40 thereon which are preferably directed sothat the stream is tangential to a circle having a radius approximatelyone-half the radius of the chamber. The feeding ports 42 are positionedin a similar manner to'those hereinbefore described but are fed from asubstantially annular manifold 44. The manifold 44 carries molten ironpreferably in a decarbonized condition, thus as the molten iron is fedinto the stream of steam 40, it is disintegrated into relativelylargesize particles and then by the continuous oxidation and attritionwithin the chamber, it is reduced this manner. materialfed into t echamber is immediate y wh rled therearound whereby particles having thegre test mass are thrown a ainst the outer walls of the chamber and arebroken u if they are sufliciently brittle. In the case of iron. ifparticles of iron are injected through ports 32. said particles bein ofrelatively lar e size. they are picked up by t e stream of steam and dueto the high temperature and oxidiz ng condition of the atmos here areoxidized at the surface thereof whereby when imoineed against the'sidesof the chamber at hi h rates of speed the oxide film breaks off in smallflakes or particles and the remaining core of iron is again pi ked uoxid zed. rotated and impin ed a ainst the sides of the chamber.Simultaneously the particles of oxide are further impinged. As theparticle size of the oxide powder is reduced, there is a tendency forthe powder which is of an imnalpable nature to be picked up or entrainedbv the outgoing-steam which is drawn oil through pipe 34 when thepressure inside the chamber exceeds the pressure in the pipe 34. Theentrained particles in the steam passing from the chamber 20 dropbygravity into discharge port 28. Thus onlythe classified and very fineparticles of oxide are taken out of the chamber. 'In this mannerdisintegration continues until a desired particle size is arrived at. Itis apparent that the velocity of the steam, design of the chamber, etc.,may be to small particles of the desired size of iron oxide. In order toprevent premature freezing of the molten iron and subsequentdifllculties in the manifold 44 and ports 42 a pair of annular gasburners 46 are provided within a suitably designed chamber 48. Theburners 48 heat the manifold to a suitable temperature to maintain themolten condition of the iron. It is apparent that the entire apparatusshould be fabricated from a high melting point metal such as high speedsteel etc., having characteristics suitable for the proposed use, suchmetal being well known in the art. In the embodiment shown in Figs. 3and 4 it is apparent that one of the steps in the process-heretoforedescribed may be eliminated since the steam jets break up the molteniron and free it and simultaneously carry out the other functions ofdisintegrating and oxidizing.

In each instance the steam used should be at an extremely hightemperature and pressure so that the chamber and'contents are heated tosubstantially the temperature of the steam. Such temperatures andpressures are best arrived at by trial since under difierent conditionsdifferent control conditions are desirable. I have found, however, thatthe steam is preferably supplied at temperatures of about 1000 F. and atpressures above pounds per square inch for the most satisfactoryresults. It is apparent that these temperatures and pressures may bevaried and that other oxidizing fluids may be simultaneously injectedinto the chamber to increase the oxidization, for example, oxygen may beincluded and it isto be understood in the appended claims that when theterm steam or "oxidizing fluid is mentioned that the inclusion of oxygenseparately or together with steam, or of other oxidizing fluidsseparately or together with steam are within the scope of my invention.

Another type of apparatus which may be used to carry out the inventionis disclosed in Fig. 5 wherein a conventional type of ball mill I isshown which is driven through a pair of gears 62 and 64, the gear 62being driven by a suitable motor (not shown). The mill is supported by aplurality of rollers 66, or other suitable supports. In this embodimentiron particles of relatively small size as obtained by passing molteniron" into a stream of water or the like, is placed within the milltogether with a number of high speed steel balls 68. The mill is thenrotated by means of the driving motor whereby the balls mill the powdertherebetween and against the sides of the chamber of the mill. In orderto obtain an oxide coating on the particles of iron, a pipe 10 isprovided in the mouth of the mill and high temperature steam isintroduced therein as an oxidizing fluid. The mill ispreferably heatedto a temperature in the neighborhood of 1,000 F. either by a pluralityof gas burners 12 or by electrical heating elements (not shown)incorporated within the walls of the mill.

Another means of obtaining the same results is to eliminate the steamjet 10 and the burner 12 and substitute a burner 14 within the mouth ofthe mill which burner produces a flame having oxidizing characteristicswhich plays directly upon the material being milled. Thus the materialis heated and simultaneously oxidized.

It will be apparent that these embodiments accomplish the same resultsas are accomplished in a centrifugal type of disintegrator and in bothof the embodiments shown in Figs. or 6, the material may be classifiedby air flotation methods, screening or other conventional well knownclassification procedures. Instead of a ball mill, a rod mill, or anyother type of attrition apparatus may be used.

The present invention is particularly applicable to the manufacture of songe iron powder in that it reduces the time period of oxidizationusually reouired. This is occasioned by the fact that as particles ofiron are oxidized, the outside coating, in effect, acts as a protectingcoating, there y retarding further oxidlzation of the article. In thepresent instance as soon as an oxide coating is obtained. it is removedthereby permitting new iron surfaces to become oxidized. In this manner,the oxide coating does not retard further oxidization of the article.Like ise the broken off particles of oxide may be further disintegratedwithin the ap aratus and drawn off without any possibility of theparticles of iron being drawn 011 unless the iron should ha pen to be ofthe desired particle size since the iron itself not being friable is notdisintegrated.

Fig. '7 is a flow chart showing the preferred method of makin s ongeiron owder. In each case a melt down furnace is utilized. However, inone embodiment of the method the molten iron is fed directly to thedisintegrator wherein disintegration and oxidation are accom lishedsimultaneously w ereas in the other embodiments t e iron is firstdisintegrated into relativelv small size particles which particles werefed to the disintegrator forfurther disintegration through oxidation andattrition. After the oxide has been classified to the desired particlesize, it is then passed through a reducing furnace under deoxidizingconditions and thereby transformed to sponge iron powder which may bestored or used as desired. It is further desirable in many cases tostore the iron oxide powder per se and only deoxidize such quantitiesthereof as are required for immediate use. In this manner iron powder isfree from oxides and thereby may be more ad-,

vantageously used in the manufacture of porous iron articles which areconveniently prepared by briquetting the iron powder into articles ofdesired shape and then sintering the briquettes so formed undernon-oxidizing conditions to form porous metal articles.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In a method of making powdered iron oxide, the steps comprising;treating particles of iron with high pressure steam at a suflicientlyhigh temperature to cause an oxide coating to be formed at the surfaceof the particles of iron, mechanically removing the oxide coating byattrition through agitation by the high pressure steam, oxidizing newlyexposed surfaces of the iron and simultaneously disintegrating theremoved oxide coating to the size desired.

2. A continuous process of making iron oxide powder, the stepscomprising; continuously supplying iron in finely divided form to adisintegrating chamber. continuously agitating said iron with oxidizingfluid at high pressure at a temperature sufficiently high for oxidizingthe surface of the iron to iron oxide, continuously removing the ironoxide from the surface of the particles of iron by attrition between theagitated particles as caused by the high pressure fluid, simultaneouslydisintegrating said iron oxide to a smaller particle size by attrition,oxidizingthe particles of iron which have had the iron oxide surfaceremoved therefrom and continuously removing the smaller sized iron oxideparticles from said chamber.

, 3. The process of making iron oxide powder the steps comprising:supplying molten iron to a circular chamber, breaking up the stream ofmolten iron by means of a stream of an oxidizing fluid at a hightemperature and under a high pressure rotating the particles of iron soformed at a sufliciently high rate of speed within the chamberforcausing the particles of iron to be thrown against the sides of thechamber, simultaneously oxidizing the surface of the iron by means ofsaid oxidizing fluid whereby a portion of the surface oxide is crackedoff of the particles each time they are thrown against the sides of thechamber, simultaneously circulating the particles of iron oxide withinthe chamber at a speed sufficiently high for causing the particles toimpinge against the sides of thechamber for disintegrating the particlesto a desired particle size, and then drawing ofi the excess fluid withthe entrained, small particles of disintegrated oxide therein.

4. The method of making com1ninuted iron oxide comprising the stepsoiimelting iron, supplying molten iron in small quantities into a zonein proximity to the periphery of a generally-circular, axially-confinedvortex chamber, simultaneously discharging an oxidizing fluid at a hightemperature and under hi h pressure into the supply of said molten metalin a manner which will cause the fluid to rotate rapidly in the chamberand simultaneously break up the su ply of molten metal to smallparticles and oxidize the surface of the particles while causing theparticles to impinge on the walls of the chamber thereby breaking oilthe oxide coating which is friable, impinging the broken oi! oxidecoating on the walls of the chamber to disintegrate the same and thendrawing oi! comminuted particles of the desired size from an inwardpoint in said chamber.

5. In a method of making iron oxide powder of desired particle size, thesteps comprising; supplying particles of relatively small size of ironto a vortex chamber causing said particles to move in acircular path ofa substantially peripherally confined narrow zone so as to cause thelarger particles of said material to be thrown outwardly against theperipheral portion of said chamber multaneously oxidizing the surface ofsaid iron particles whereby said oxidized surface is broken off theparticles uponimpingement thereof against the confining walls of saidchamber, comminuting the oxide particles by further impingement thereofdue to tangential movement thereof from said circular path,simultaneously reoxidizing the surface of the particles of iron by meansof said fluid, and causing a central classifying action of saidparticles whereby the flnely comminuted particles of the oxidem'o'veinwardly in substantially the plane of said zone and pass oil.from the central portion of said zone.

8. In a method of making highly comminuted iron oxide, the steps of,supplying iron to a generally circular vortex chamber adjacent theperiphery thereof injecting a high temperature. high pressure oxidizingfluid to said chamber at a plurality of points in such a manner as tocause said iron to be moved in a circular path around said chamber andfor simultaneously oxidizing the surface of the particles of iron so asto cause the larger particles of said oxi ized iron to be thrownoutwardly against the peripheral portion of the chamber whereupon theoxidized surface thereof is broken oil by impingement of the particlesagainst the wall of the chamber, circulating the iron and the broken of!oxide particles, and removing the comminuted oxide when sufllcientlyline through the central portion of said chamber.

CECIL A. MANN.

